Conditioning effects like those resulting from exercise training may be produced by repeated infusions of a catecholamine, dobutamine. Exercise conditioning also has been shown to promote coronary collateralization in animals with coronary artery occlusion. We propose to study 1) chronic effects of dobutamine on cardiac reserve and coronary collateral ormation in dogs with coronary artery occlusion, 2) acute effects of dobutamine on systemic hemodynamics and regional blood flows in dogs with either acute coronary occlusion or congestive heart failure, and 3) chronic effects of dobutamine on cardiac reserve in dogs with congestive heart failure. Coronary artery occlusive lesions will be produced by placing an Ameroid constrictor around the left anterior desending coronary artery along with a fixed stenosis of the left circumflex coronary artery. Experimental heart failure will be produced either by aorto-caval fistula or by progressive pulomonary stenosis and tricuspid avulsion. Cardiac reserve function will be assessed by measuring the animals' hemodynamic and metabolic responses to treadmill exercise, and by obtaining left ventricular pressure function curves. Coronary collateral flows and organ blood flows will be measured by the radioactive microsphere technique. Ultrasonic dimension gauges will also be used in these experiments to measure left ventricular wall thickness and chamber dimensions. These studies will demonstrate whether long-term dobutamine infusions can improve baseline cadiac performance in experimental congestive heart failure and ischemic cardiac injury and whether a cardiac conditioning effect like that resulting from physical training in normal dogs is observed. In addition, infusions of dobutamine in experimental acute myocardial infarction and congestive heart failure are expected to have acute effects upon regional blood flow distribution, and it will be determined whether renal blood flow is preserved under these conditions. These experiments may provide information which will encourage new approaches to the management of patients with ischemic heart disease or congestive heart failure.